On the fast quenching of young low-mass galaxies up to z $\sim$ 0.6: new spotlight on the lead role of environment

Abstract

We investigate the connection between environment and the different quenching channels that galaxies are prone to follow in the rest-frame NUVrK colour diagram, as identified by Moutard et al. (2016b). Namely, the fast quenching channel followed by $young$ low-mass galaxies and the slow quenching channel followed by $old$ high-mass ones. We make use of the >22 deg${}^2$ covered the VIPERS Multi-Lambda Survey (VIPERS-MLS) to select a galaxy sample complete down to stellar masses of $M_{\ast }>10^{9.4}{M}_{\odot }$ at $z<0.65$ ($M_{\ast }>10^{8.8}{M}_{\odot }$ at $z<0.5$) and including 33,500 (43,000) quiescent galaxies properly selected at $0.2<z<0.65$, while being characterized by reliable photometric redshifts (${\sigma }_{\delta z/(1+z)}\le 0.04$) that we use to measure galaxy local densities. We find that (1) the quiescence of low-mass [$M_{\ast }\le 10^{9.7}{M}_{\odot }$] galaxies requires a strong increase of the local density, which confirms the lead role played by environment in their fast quenching and, therefore, confirms that the low-mass upturn observed in the stellar mass function of quiescent galaxies is due to $environmental$ $quenching$. We also observe that (2) the reservoir of low-mass star-forming galaxies located in very dense regions (prone to environmental quenching) has grown between $z\sim 0.6$ and $z\sim 0.4$ whilst the share of low-mass quiescent galaxies (expected to being environmentally quenched) may have simultaneously increased, which would plead for a rising importance of $environmental$ $quenching$ with cosmic time, compared to $mass$ $quenching$. We finally discuss the composite picture of such environmental quenching of low-mass galaxies and, in particular, how this picture may be consistent with a $delayed$-$then$-$rapid$ quenching scenario.

14 pages, 5 figures, accepted for publication in MNRAS; published version